In systems for recovering refrigerant from refrigeration equipment under service, there have been a number of techniques proposed for removing or purging air from the recovered refrigerant. For example, in a system in which the refrigerant is pumped to a storage container by a compressor or liquid refrigerant pump, an air purge chamber may be connected between the refrigerant compressor or pump and the storage container for accumulating refrigerant in liquid phase at a lower portion of the chamber, and trapping air and other non-condensibles over the liquid refrigerant at the upper portion of the chamber. The trapped air and non-condensibles may be automatically or manually purged through a suitable valve when pressure becomes excessive.
U.S. application Ser. No. 08/100,424, assigned to the assignee hereof, now U.S. Pat. No. 5,367,886, discloses a refrigerant handling system that includes an air purge chamber and a refrigerant pump for directing refrigerant into the air purge chamber so that the refrigerant collects in liquid phase at a lower portion of the chamber while air and other non-condensibles collect in vapor phase at the upper portion of the chamber over the refrigerant. A purge valve is connected to the upper portion of the chamber for automatically or manually purging air and other non-condensibles from the chamber. A refrigerant outlet is positioned at the lower portion of the chamber for drawing liquid phase refrigerant from the chamber. A minimum level of liquid phase refrigerant is maintained at the lower portion of the chamber to isolate the outlet from the vapor space, and thereby prevent removal of air and other non-condensibles from the chamber through the outlet. Minimizing the liquid volume relative to the vapor volume reduces the amount of non-condensibles dissolved in the liquid phase refrigerant. A clearing valve is connected between the refrigerant pump and the air purge chamber, and may be selectively set in a clearing mode of operation such that the pump clears all refrigerant from the air purge chamber and directs such refrigerant to a refrigerant storage container.
In air purge systems of the described character, the vapor space above the liquid refrigerant in the air purge chamber will contain some refrigerant vapor, with the amount of such vapor depending upon the type of refrigerant, refrigerant temperature and vapor pressure within the air purge chamber. Thus, when the air purge chamber is vented to atmosphere, a small amount of refrigerant will be released into the atmosphere, deleteriously affecting the environment and necessitating the expense of make-up refrigerant. It is therefore a general object of the present invention to provide a system and method for refrigerant handling with air purge capabilities in which release of refrigerant vapor is prevented during the purging operation. Another object of the present invention is to provide a refrigerant handling system and method of the described character that include facility for clearing refrigerant from the handling system components, including the air purge chamber, preparatory to service on the system or employing the system in conjunction with a different refrigerant, and thereby preventing venting of the refrigerant to the atmosphere and inadvertent mixing and contamination of different types of refrigerant.
A refrigerant handling system in accordance with a presently preferred embodiment of the invention includes an air purge chamber and a refrigerant pump for directing refrigerant into the air purge chamber so that the refrigerant collects in liquid phase at a lower portion of the chamber while air and other non-condensibles collect in the vapor space at the upper portion of the chamber over the liquid refrigerant. A purge valve is connected to the upper portion of the chamber for automatically or manually purging air and other non-condensibles from the chamber. A refrigerant outlet is positioned at the lower portion of the chamber for drawing liquid phase refrigerant from the chamber. Desiccant adsorbent material is disposed in a canister connected to the upper portion of the air purge chamber for adsorbing refrigerant vapor in air passing through the canister. The desiccant adsorption material thus prevents venting of refrigerant vapor with non-condensibles from the air purge chamber.
In the preferred embodiment of the invention, the refrigerant pump mechanism comprises a compressor connected through a condenser to the air purge chamber, so that the condenser at least partially condenses refrigerant prior to entry into the air purge chamber. A check valve is connected at one end to a liquid refrigerant outlet from the air purge chamber, and at a second end between the condenser and the chamber inlet. The air purge chamber, the condenser and the desiccant canister may be selectively cleared of refrigerant by connection to the inlet of the compressor, so that operation of the compressor draws refrigerant from the condenser, and from the air purge chamber and desiccant canister through the check valve and the condenser. During such clearing mode of operation, the compressor outlet is connected through a refrigerant heat exchange coil disposed in the desiccant canister for heating the desiccant material and thereby promoting release of refrigerant adsorbed by the material.